The present invention relates to turbine buckets. Turbine buckets, in general, are the rotating blades in a turbine engine that convert the flow of a working fluid through the turbine into mechanical energy. More particularly, but not by way of limitation, the present invention relates to an improved airfoil shape for turbine buckets. While the invention disclosed herein is described and intended for use in a gas turbine engine, as discussed in more detail below, a scaled design may be used effectively in a steam turbine or aircraft turbine engine.
The working fluid of a gas turbine engine generally comprises the resulting flow of hot gases from the combustion of a fuel. The flow of hot gases is directed through the turbine section of the engine, which generally includes multiple stages of turbine buckets. Each bucket includes a bucket airfoil or airfoil, which is the part of the bucket that interacts with the flow of working fluid. Because of the shape of the airfoil, the working fluid induces the stage of buckets to rotate about the rotor, thus converting the energy of the working fluid into mechanical energy.
As one of ordinary skill in the art will appreciate, the design and shape of the airfoils in the multiple stages may significantly impact the overall performance of the turbine. The airfoils for each of the stages have a unique set of design requirements, which must be met for turbine performance objectives, for example, overall engine efficiency, to be satisfied. In some cases, minor variances in airfoil design and shape may have significant effects on engine operating efficiency or the loading characteristics of the turbine buckets during operation. Of course, as energy costs rise, as they inevitably seem to do, designing turbine engines that promote efficiency is a continuing and important objective. As a result, there is a continuing need for improved airfoil shapes that provide efficient turbine operation through the several stages of a turbine engine.